The meteoric rise of Sen. Bernie Sanders (I-Vermont) has rocked
the political establishment and infused competition into the
Democratic presidential race.

Sanders has held a lead over
the Democratic field in New Hampshire, the first primary
state, for more than a month. And he has continued to close in on
front-runner Hillary Clinton in Iowa, a state that helped affirm
the legitimacy of then-Sen. Barack Obama's candidacy.

But the self-proclaimed Democratic socialist still hasn't
overcome his primary problem: his inability to seriously grow his
support beyond white voters.

A new CNN/ORC poll of Nevada and South Carolina out on Monday
amplified that problem. The poll showed Clinton with a commanding
lead among Democratic voters in South Carolina and Nevada,
the third and fourth nominating states, which are markedly
more diverse than Iowa and New Hampshire.

Without Vice President Joe Biden in the race, Clinton
led among likely Democratic primary voters in South Carolina
with 70% of the vote, while Sanders garnered only 20%. Even with
Biden in the race, Clinton was still ahead in the Palmetto
State — with 49% support, compared with Biden's 24% and
Sanders' 18%.

Sanders fared better in Nevada, but he still
trailed Clinton significantly. Clinton received the
support of 56% of likely Democratic voters in Nevada, while
Sanders grabbed 36%. If Biden were to enter the race,
the poll found that 50% of voters would support Clinton, 34%
would favor Sanders, and 12% would pick Biden.

Clinton was the overwhelming preference of black voters in
South Carolina. Without Biden in the race, 84% of black voters in
South Carolina supported Clinton, compared with only 7% who
backed Sanders. Black voters made up the majority of
Democratic primary voters in South Carolina in 2008, when Obama
won the state.

"If Sanders wins Iowa or New Hampshire, it will build a lot of
momentum for him that will help in the states that follow, but
he's still going to struggle in places like South Carolina with
large black populations and Nevada with large Hispanic
populations unless he improves his appeal to nonwhite voters,"
Tom Jensen, the director of the firm Public Policy Polling,
told Business Insider earlier this year.